POLR3B and leukodystrophy: A subset of leukodystrophies named RNA polymerase III (Pol III)-related leukodystrophy or 4H (hypomyelination, hypodontia, and hypogonadotropic hypogonadism) leukodystrophy (MIM 607694, 614381)3 was found to be caused by biallelic pathogenic variants in genes encoding specific subunits of the enzyme Pol III, namely POLR3A, POLR3B, POLR3K, and POLR1C4–9.